PO had no clue what mods have been done to this car.. Please help - Miata Turbo Forum - Boost cars, acquire cats.

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Old 02-22-2014, 04:25 PM   #1
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Default PO had no clue what mods have been done to this car.. Please help

Ok.. I picked up this 97 STO (1.8L) with a homebrew kit for $2600. It's not terrible, but not great either. PO did not know any of the modifications or specifications. All he knows is that it was "turbo" and "fast". The car is currently shuttling at 3,500-4,000 rpms under load. Not sure if this is fuel or boost related. Had it checked out at a dyno shop and the car is running extemely lean (16/1 in full boost ~7 psi). Was rightfully instructed avoid boosting until I can get the car tuned. It has a megasquirt PNP, and I just got the cable in today. I am hoping that a base map will help even things out and get a proper fuel mixture. I do not know injector size, PO claimed they were 'oversized'. I have never tried to tune a car and I am a big ol' noob, could really use some help!

Ideally I would like to get the car running well enough to not do any damage and still be able to have fun. I also want to cut down on my dyno time as much as possible so I would like to have most of the mapping done before I get there.

My questions:
How do I find out what size my injectors are?
Will I blow up my car using a base map?
Any tips for a tuning noob?

Thanks in advance!

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PO had no clue what mods have been done to this car.. Please help-bqmzgfm.jpg  

Last edited by CantSleep_BuildinStuff; 02-22-2014 at 06:02 PM.
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Old 02-22-2014, 04:27 PM   #2
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Post some detailed pictures, and when you can post the tune file.
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Old 02-22-2014, 04:42 PM   #3
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Post some detailed pictures, and when you can post the tune file.
I don't know how to post a tune file. I will figure it out though. o_o
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Old 02-22-2014, 04:47 PM   #4
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I also strongly encourage you to either not drive the car, or tie the wastegate open until you have the tune sorted out.
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Old 02-22-2014, 04:55 PM   #5
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Does it have a wideband?

Yeah.
I also suggest that you just park the car until you know what you're doing.
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Old 02-22-2014, 05:18 PM   #6
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Does it have a wideband?

Yeah.
I also suggest that you just park the car until you know what you're doing.
No wideband yet. It's the only car I have other than my motorcycle at the moment. Parking it is unfortunately not an option as I have work and class. I am trying to get everything sorted so I can get it tuned at a shop. I just want to get it safe to drive for now
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Old 02-22-2014, 05:24 PM   #7
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Easy enough, tie the wastegate open. Do not go into boost. It can be driven, but gingerly. You need to get a wideband before anything else.

I can't believe it's lived this long if those were your actual AFRs.
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Old 02-22-2014, 05:28 PM   #8
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Easy enough, tie the wastegate open. Do not go into boost. It can be driven, but gingerly. You need to get a wideband before anything else.

I can't believe it's lived this long if those were your actual AFRs.
The PO said he turned down the spring inside the wastegate because it was at 16 psi, and he wanted better gas mileage. Then he had trouble with it idling, so he 'turned up' the idle. : \

edit: Also, any tips for tying the wastegate open?
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Old 02-22-2014, 05:36 PM   #9
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Internal or external? This is why we need pics. We can't really help if we don't know what you have.
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Old 02-22-2014, 05:39 PM   #10
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Old 02-22-2014, 06:01 PM   #11
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You found it!
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Old 02-22-2014, 09:29 PM   #12
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For your injectors, you will have to pull them and look at the numbers.
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Old 02-22-2014, 10:41 PM   #13
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Host the pictures on here please. Take pictures of the downpipe (the exhaust pipe that comes out of the back of the turbo).

Try and get under the car and check for things that plug into the downpipe that have wires.

Though it is not impossible, IF it truly has a megasquirt I have a hard time believing there isn't an oxygen sensor. You also need to get a laptop hooked up to that megasquirt and post up the tune. And disconnect the wastegate actuator arm from the flapper and wire it wide open until you get it it sorted out.

Check if the vacuum line is connected to the megasquirt and also check where it connected to in the engine bay.

Additional pictures that would be helpful:
- Pictures of the megasquirt itself
- pictures of where the vacuum line is plugged into on your manifold
- pictures of where your wastegate is getting it's vacuum signal (nevermind... i see)
- take off the turbo blanket if you can without destroying it. Take a bunch of pictures from various angles so we can see the exhaust manifold. This isn't important for tuning but it will give us an idea of what kind of parts were installed.

What cable were you waiting for? Have you downloaded tunerstudio? Once you have tunerstudio installed on laptop and cable connecting the two (vehicle powered up but not necessarily running), create a new project and when it will ask you for ECU definition. You can have tunerstudio get that from the megasquirt. Then, allow the tune on the car to overwrite the tune on your laptop. Is there anyone in the birmingham area that can walk you through this?

Btw, you don't necessarily need a base map. We need to see what your current tune has in it first though.

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Old 02-23-2014, 12:20 AM   #14
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Originally Posted by Tekel View Post
For your injectors, you will have to pull them and look at the numbers.
Numbers are printed on it? Ok. I'll pull them and have a look.

I will also take some more pictures tomorrow.

Here's what I've done so far:
-Downloaded Tunerstudio
-Uploaded the base map for a 96-97 miata from megasquirt
-Used live tuning and autotune to further dial the car in

The car is running like a scalded dog right now, but still unsure of my AFR in and out of boost. My local shop offers installation of an O2 sensor bung for $75. Still figuring out how to install a standalone wideband display. Car is still idiling really high (approx. 2,000 RPM), oscillating, and is shuttling some at high RPMs. I only ran tunerstudio autotune twice before I had to quit (getting late, neighbors complaining). I will continue to let it map itself. I am having a friend come over tomorrow to help me adjust timing.

I hope I am not being naive in letting Tunerstudio sort the car out, but it seems to be working for now.
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Old 02-23-2014, 12:49 AM   #15
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Wait, how are you auto-tuning without an o2 sensor?
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Old 02-23-2014, 01:05 AM   #16
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Wait, how are you auto-tuning without an o2 sensor?
I have O2 sensors, I just want another bung so I can install a wideband and have my mixture displayed as I boost my face off
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Old 02-23-2014, 01:56 AM   #17
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Ok, you have an o2 sensor, but only a narrowband? You can't tune anything other than stoich on a narrowband.

This is how it was explained to me...

Say a narrowband is 1-3 volts... (I may be off on the actual volts)

When you AFR is between 14.3 and 15.1 the voltage reads 2 volts. When the voltage is above 2.2 volts you know your AFR is higher than 15.1, when it reads lower than 1.8 volts your narrowband knows it's lower than 14.3. That's all. Period. It is fundimentally unsafe to (auto)tune without a wideband o2 sensor.

IF you have a wideband that doesn't have a display, then you can keep on tuning.

EDIT: You don't need a bung installed for wideband, you can install it in the place of one of your existing o2 sensors. Then you need to run the 5v wire to the megasquirt and setup the MS for use with the wideband including calibration...
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Old 02-23-2014, 02:09 AM   #18
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Dude. You're going to blow your car up. You have every reason to believe you're about to blow the motor running super lean. Stop boosting it.
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Old 02-23-2014, 11:11 AM   #19
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more pics please. (of entire car too)


parts shown look like ebay parts.
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Old 02-23-2014, 11:18 AM   #20
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Quote:
Originally Posted by Chiburbian View Post
Ok, you have an o2 sensor, but only a narrowband? You can't tune anything other than stoich on a narrowband.

This is how it was explained to me...

Say a narrowband is 1-3 volts... (I may be off on the actual volts)

When you AFR is between 14.3 and 15.1 the voltage reads 2 volts. When the voltage is above 2.2 volts you know your AFR is higher than 15.1, when it reads lower than 1.8 volts your narrowband knows it's lower than 14.3. That's all. Period. It is fundimentally unsafe to (auto)tune without a wideband o2 sensor.

IF you have a wideband that doesn't have a display, then you can keep on tuning.

EDIT: You don't need a bung installed for wideband, you can install it in the place of one of your existing o2 sensors. Then you need to run the 5v wire to the megasquirt and setup the MS for use with the wideband including calibration...

I will find a wideband and install it ASAP. There are not many performance shops around here, so I will proabably have to wait until tomorrow.
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